Conus striatus is a venomous fish-hunting cone snail from the Indo-Pacific region that makes use of excitatory paralysis to subdue its prey. Peptides in the snail's venom target neurons in the prey, resulting in unregulated firing. The molecular mechanisms and protein targets of these venom peptides are unclear. The objective of this proposal is to identify novel excitatory peptides in the injected venom of C onus striatus and related cone snails and, using an electrophysiological approach, clarify their targets and mechanism of action. Two predominant peptides of the Conus striatus venom have been purified by reverse-phase HPLC and assayed for activity using a frog neuromuscular preparation. Both peptides recapitulate the spastic paralysis activity observed for the injected venom. These peptides induce repetitive firing of nerve termini and nodes of Ranvier in response to a single electrical stimulus of the nerve. Additionally, the peptides initiate spontaneous repetitive firing. Using voltage-clamp methodologies on cultered cells as well as on oocytes expressing specific channel isoforms, I will seek to identify the molecular target for each of the two Conus striatus peptides. Examination of the kinetic properties of the ion channels will provide insight as to the molecular mechanisms of action of these peptides. The venom of a closely-related snail, Conus catus, also causes excitatory' paralysis when tested on the frog neuromuscular preparation. Three active fractions have been identified in the venom of this snail and the active peptides will also be identified as part of this proposal allowing for future structure-function and comparative evolutionary studies. In addition to learning about the specific roles of venom constituents and their target channels, these studies should shed insight on ion channel function.